KANSAS CITY, Mo., March 25 (Reuters) - Missouri officials were preparing on Tuesday to execute a man convicted of abducting, raping and strangling a teenage girl who was working as a gas station attendant.

Jeffrey Ferguson, 59, was twice convicted for killing 17-year-old Kelli Hall, who he kidnapped with an accomplice as she ended her evening shift at a metropolitan St. Louis service station on Feb. 9, 1989. The girl's naked body was found less than two weeks later.

Ferguson is scheduled to be executed at 12:01 a.m. local time on Wednesday at a state prison in Bonne Terre, Missouri. He would be the third man executed in Missouri this year.

Ferguson's first conviction in 1992 was overturned due to a problem with the jury instructions. He was convicted in a second trial and again sentenced to death.

Attorneys for Ferguson have filed several appeals to try to delay or halt his execution. His attorneys argue, among other things, that an FBI agent gave false and misleading testimony at his trial.

"Kelli Hall was only 17 when she was abducted from her workplace, raped and brutally murdered," Nixon said in a statement. "Her life, so full of promise, was brutally taken from her and her family."

Eric Slusher, a spokesman for the state attorney general's office, said there was nothing currently prohibiting the state from carrying out the sentence as planned.

According to prosecutors, Ferguson had been out drinking at a bar with a friend and then went to meet another friend at the gas station where Hall was ending her shift. Hall was checking the fuel levels in the station tanks when a witness saw her forced into the back seat of a vehicle by a white male.

The next day a maintenance worker found Hall's coat and clothes discarded at the side of the road. A farmer later found her battered frozen body hidden in a machinery shed.

Ferguson's execution comes at a time when Missouri, and several U.S. states, are under fire for turning to lightly regulated compounding pharmacies for their lethal injection drugs. Major pharmaceutical companies have stopped allowing sales of their drugs for executions, leaving U.S. states scrambling to come up with alternatives.

Two executions planned for March in Oklahoma were postponed until April after the state said it was having trouble obtaining the drugs it needs to perform executions.

Advocates for inmates say drugs from compounding pharmacies can lack purity and potency and cause undue suffering in violation of the U.S. Constitution's protections against cruel and unusual punishment.

Ferguson is one of a group of Missouri inmates who sued state officials in 2012 in a challenge to the constitutionality of the state's execution protocols. The case is set for trial Sept. 15.

Missouri has since made a series of changes to its execution protocols. The state is now under scrutiny for adding layers of secrecy to its practices, including its efforts to source drugs from compounding pharmacies. The state has also been criticized for carrying out executions while appeals are awaiting court review. (Reporting by Carey Gillam in Kansas City; Editing by Ken Wills and Eric Walsh)